Charger for electric vehicles with distributed power converter arbitration

ABSTRACT

The present application relates to a charger for electric vehicles, comprising at least two power exchange ports for vehicles, each port comprising a data communication connection for at least receiving a power request from a vehicle, and a power exchange connection for delivering power to a vehicle; at least one grid connection for receiving electric power; a data communication bus, for communicating the power request from the vehicles to a plurality of autonomously controllable power converters, each for converting power from the grid connection to a suitable level for charging a vehicle; and each of the power converters comprises a data communication device, connected to the data bus, and configured for receiving power requests from vehicles; and configured for indicating its available power via the data bus.

BACKGROUND

The present invention relates to a charger for electric vehicles, morein particular to a charger comprising multiple power converters.

Chargers for electric vehicles comprising multiple power converters areknown in the art. An advantage of the use of multiple converters in onecharger is that the number of active converters can be set according toa momentary power demand. Power converters in use may be operated in anenergy efficient, often maximal power of duty cycle mode.

An example of such charger is given in the U.S. Pat. No. 7,135,836,wherein a vehicle charger with multiple power converters and multiplepower exchange ports for batteries is disclosed. The converter comprisesa central, so called system level, controller and interface forcontrolling the power levels at which the converters function.

Although the above described topology fulfils a certain need, increasingcommunication facilities of electric vehicles have raised a demand for amore advanced method of control for a charger for electric vehicles.

The 2009 IEEE proceedings “Distributed Control of Parallel AC to DCConverter” proposes a different way of controlling power converters ofan AC/DC converter, wherein each converter module comprises its owncontroller. The power converters outputs are used for powering a commonload, which is not necessarily an electric vehicle that requires quickcharging. This system however does not enable charging of multiplevehicles at one time.

SUMMARY

It is a goal of the present invention to provide such improved powerconverter, or at least to provide a useful alternative to the state ofthe art chargers for quick charging electric vehicles.

The invention thereto proposes a charger for electric vehicles,comprising at least two power exchange ports for vehicles, each portcomprising a data communication connection for at least receiving apower request from a vehicle, and a power exchange connection fordelivering power to a vehicle at least one grid connection for receivingelectric power, a data communication bus, for communicating the powerrequest from the vehicles to a plurality of autonomously controllablepower converters, each for converting power from the grid connection toa suitable level and wave-form for charging a vehicle, wherein each ofthe power converters comprises a data communication device, connected tothe data bus, and configured for receiving power requests from vehicles;and configured for indicating its available power via the data bus.

By providing each of the power converters with a communication device,an adequate and efficient communication with a vehicle to be charged maybe obtained. The charger according to the present invention provides theadvantage that vehicles may have direct communication with a powerconverters controller, which enables the charger to continuously adaptitself to optimal settings for that specific moment and/or combinationof vehicles to be charged.

A further advantage of the charger according to the present invention isthat software maintenance of the controllers of the power converters ismade easier, since all controllers can be addressed directly. Withrespect to the state of the art patent mentioned above one advantage isthat there is no need for a master controller anymore. The chargeraccording to the present invention may be operated as follows. When oneor more vehicles connect to the charger in order to be charged, the sumof power requested by vehicles at power exchange ports of the charger isdetermined, as well as the sum of power available by power converterscomprised by the charger. If the sum of the power requested is largerthan the sum of the available power, the available power of at least onepower converter is allocated to the power exchange port a requestingvehicle is coupled to. Then the remaining sum of power available bypower converters comprised by the charger is determined, and if the sumof the power requested is larger than the sum of the available power; anegotiation is performed with the vehicle. Next, the available power ofat least one power converter is delivered to the power exchange port arequesting vehicle is coupled to.

To fulfil the request of the vehicle, the controller chooses the powerconverters to deliver this power. This choice is made using adeterministic algorithm. Since all controllers use the same selectionalgorithm, they know each other's choices without the need for furthercommunication.

In an embodiment, the data communication connections of the powerexchange ports are provided with a data communication device, that isconfigured for retrieving a power request from a vehicle, making therequest available to the controllable power converters via thecommunication bus and receiving available power indications from thepower converters.

A vehicle to be charged may be coupled to a power exchange port and acorresponding data communication port of the charger. Then the datacommunication device of the port the vehicle is coupled to receives arequest from the vehicle, comprising requirements the vehicle sets tothe charging, like a required power, a maximum duration of the charging,and protocols according to which the vehicle is able to be charged.

In the above example, the vehicle is “leading”, that is: the chargerresponds to a demand from a vehicle. It is also possible that thecharger communicates the available power to a vehicle and that thevehicle then indicates how much of the available power it requires. Inthat case the charger is operated as follows, wherein the datacommunication connections of the power exchange ports are provided witha data communication device, that is configured for receiving availablepower indications from the power converters, making the requestavailable to the vehicle via the communication bus and retrieving apower request based on the available power from a vehicle.

In yet a further embodiment, the data communication devices areconfigured for determining if at least one power converter has poweravailable for at least partly fulfilling a request from a vehicle;coupling a power output of at least one power converter to a powerexchange connection of a power exchange port for a vehicle if power isavailable; and negotiating power conversion settings with theautonomously controllable power converters in response to a powerrequest from a vehicle. In such way, the request from a vehicle isdirectly and independently dealt with by the port that the vehicle isconnected to.

In a further embodiment, the data communication devices are configuredfor coupling power outputs of available power converters to a powerexchange connection until the power request is fulfilled or until nomore power converters are available.

When a power request is received from a vehicle, the communicationdevice communicates the request via the communication bus, and it isreceived by all power converters. The controller estimates whether theconverters can deliver (a part of) the requested power. Since a galvanicseparation is required between multiple vehicles coupled to one charger,a power converter can only be coupled to one power exchange port. Whenone power converter can deliver the requested power, it indicates so,and it is coupled to the power exchange port. When the requested poweris larger than the power that can be delivered by one power converter, asecond and further converter may be coupled to the power exchange port.In such case one or more number of power converters may operate at theirmaximum power level and/or duty cycle, and one last power converter maybe operated on a power level below its maximum. This is done forobtaining a maximum efficiency, since power converters normally operatemost efficient at their maximum power level and/or full duty cycle.

In yet a further embodiment, the data communication devices areconfigured for verifying if there are available power converters after apredetermined time interval or after a predetermined event when a powerrequest was or is more than a maximum power available from a powerconverter; and if there are available power converters, coupling a poweroutput of at least one of such power converters to the power exchangeconnection of the power exchange port for the vehicle that requests thepower.

If a vehicle arrived at a time that the power it requests was notavailable, and it was set to a lower level than desired, it isadvantageous when the available power is determined on a regular basis,so new negotiations can be started as soon as a change in the situation(for instance because a vehicle has left) occurs.

In a further embodiment the charger comprises a data storage coupled tothe data communication bus, the data storage comprising systemlimitation data, such as a power limitation of the grid connection, peakshaving requirements or energy costs.

Furthermore a communication port for communication with the power gridmay be present.

BRIEF DESCRIPTION OF THE DRAWINGS

The application will be elucidated into more detail with reference tothe following figures:

FIG. 1 shows a schematic view of a charger according to the presentinvention;

FIGS. 2a-2k give a detailed example of a sequence of practicalsituations at the charger.

DETAILED DESCRIPTION

FIG. 1 shows a schematic view of a charger 1 according to the presentinvention, comprising two power exchange ports 2, 3 for vehicles 4, 5,each port comprising a data communication connection 2 a, 3 a for atleast receiving a power request from a vehicle, and a power exchangeconnection 2 b, 3 b for delivering power to a vehicle; a grid connection6 for receiving electric power, a data communication bus 7, forcommunicating the power request from the vehicles to a plurality ofautonomously controllable power converters 8, 9, 10, each for convertingpower from the grid connection to a suitable level and wave-form forcharging a vehicle, wherein each of the power converters comprises adata communication device 8 a, 9 a, 10 a, connected to the data bus 7,and configured for receiving power requests from vehicles 4, Sand forindicating its available power via the data bus 7.

Data bus 7 provides a way to share relevant information from the powermodules, vehicle interfaces and backend interface. Information is sharedin such a way that these mentioned devices have up to date information.With this information specific choices are being made such as allocationof power modules to vehicle interfaces.

The data communication connections of the power exchange ports areprovided with a data communication device 2 c, 3 c, that is configuredfor retrieving a power request from a vehicle, making the requestavailable to the controllable power converters via the communication bus7 and receiving available power indications from the power converters 8,9, 10.

The charger further comprises a data storage 11 coupled to the datacommunication bus 7, the data storage comprising system limitation data,such as a power limit of the grid connection, peak shaving requirementsor energy costs, as well as a communication port 11 a for communicationwith the back-end of the power grid 12.

The data communication devices 2 c, 3 c, 8 a, 9 a, 10 a are configuredfor determining if at least one power converter has power available forat least partly fulfilling a request from a vehicle, coupling a poweroutput of at least one power converter to a power exchange connection ofa power exchange port for a vehicle by means of a matrix with switches13 if power is available and negotiating power conversion settings withthe autonomously controllable power converters in response to a powerrequest from a vehicle.

The data communication devices 2 c, 3 c, 8 a, 9 a, 10 a are configuredfor coupling power outputs of available power converters to a powerexchange connection until the power request is fulfilled or until nomore power converters are available.

Furthermore the data communication devices 2 c, 3 c, 8 a, 9 a, 10 a areconfigured for verifying if there are available power converters after apredetermined time interval or after a predetermined event when a powerrequest was or is more than a maximum power available from a powerconverter and if there are available power converters, coupling a poweroutput of at least one of such power converters to the power exchangeconnection of the power exchange port for the vehicle that requests thepower.

FIG. 2 shows a block diagram of a method according to the presentinvention. In general, the method comprises the steps of determining thesum of power requested by vehicles at power exchange ports of thecharger, determining the sum of power available by power converterscomprised by the charger, if the sum of the power requested is largerthan the sum of the available power, and allocate the available power ofat least one power converter to the power exchange port a requestingvehicle is coupled to, such that the power request of said vehicle ismet, and determine the remaining sum of power available by powerconverters comprised by the charger. If the sum of the power requestedis larger than the sum of the available power a negotiation with thevehicle is performed and available power of at least one power converteris allocated to the power exchange port a requesting vehicle is coupledto.

FIGS. 2a-2k give a detailed example of a sequence of practicalsituations at the charger.

FIG. 2a shows an initial situation wherein electric vehicle EV1 requestsmaximum DC power from the charger. Vehicle interface 1 sends requests tothe power modules and the back-end interface for the available DC power.

FIG. 2b shows a situation wherein each of the power is rated to 20 kWand 3 power modules are available. A dynamic grid limit is 50 kW, so theavailable max DC power is 50 kW as well.

FIG. 2c shows that electric vehicle EV1 starts with a DC power demand of40 kW. The vehicle interface 1 sends set points to two of the powermodules. Electric vehicle EV1 is charged.

FIG. 2d shows that electric vehicle EV2 arrived later than electricvehicle EV1. Electric vehicle EV2 requests the maximum DC power from thecharger. Vehicle interface 2 sends requests to the power modules and theback-end interface for the available DC power.

FIG. 2e shows that each of the power modules is rated to 20 kW and onepower module is available, the others are used by vehicle interface 1.The dynamic grid limit is 50 kW, so the maximum available DC power 10kW.

FIG. 2f shows that electric vehicle EV2 starts with a DC power demand of10 kW. The vehicle interface 2 sends set points to one of the powermodules. Electric vehicle EV2 is charged.

FIG. 2g shows that electric vehicle EV1 and 2 are being charged. Thepower demand of electric vehicle EV1 is decreased to 20 kW, thereforepower module 2 is released by vehicle interface 1.

2 h The availability of power module 2 is synchronized with interface 2,based on the available DC power a new max DC power (30 kW) is send toelectric vehicle EV2.

2 i Electric vehicle EV2 increases its DC power demand to 30 kW. Thevehicle interface 2 send set points to two of the power modules (PM2 andPM3). Electric vehicle EV2 is charged with higher power.

FIG. 2j shows that a new limit (60 kW) is received from the back-endserver of the grid operator. The new limit is synchronized with thevehicles interfaces. The maximum available DC power communicated to thevehicles are 20 kW (EV1) and 40 kW (EV2).

FIG. 2k shows that electric vehicle EV2 increases its DC power demand to40 kW. Electric vehicle EV2 is charged with higher power.

The invention claimed is:
 1. A method for operating a charger forelectric vehicles, comprising: determining a sum of power available bypower converters of the charger; communicating the sum of the poweravailable to a vehicle connected to a power exchange port of thecharger; determining a sum of power requested by vehicles at powerexchange ports of the charger; if the sum of the power requested islarger than the sum of the power available, perform a negotiation withthe vehicle; if the sum of the power requested is larger than the sum ofthe power available power, allocate the power available of at least onepower converter to the power exchange port a requesting vehicle iscoupled to, such that the power request of the vehicle is met;determining any remaining sum of power available by power converters ofthe charger, allocating the power available of at least one powerconverter to the power exchange port a requesting vehicle is coupled to.2. The method according to claim 1, comprising: allocate the poweravailable of multiple power converters to the power exchange port arequesting vehicle is coupled to, such that the power request of thevehicle is met, wherein a group of power modules is paralleled.
 3. Amethod for operating a charger for electric vehicles, comprising thesteps of: determining a sum of power requested by vehicles at powerexchange ports of the charger; determining a sum of power available bypower converters of the charger; if the sum of the power requested islarger than the sum of the power available, allocate the power availableof at least one power converter to the power exchange port a requestingvehicle is coupled to, such that the power request of said vehicle ismet; determining a remaining sum of power available by power convertersof the charger; if the sum of the power requested is larger than the sumof the power available, perform a negotiation with the vehicle, andallocate the power available of at least one power converter to thepower exchange port a requesting vehicle is coupled to.
 4. The methodaccording to claim 3, comprising: allocate the power available ofmultiple power converters to the power exchange port a requestingvehicle is coupled to, such that the power request of the vehicle ismet, wherein a group of power modules is paralleled.